rusty vango

after replacing my injectors . i noticed my alt not charging. but when i had it tested at auto zone . it worked.??? what would cause such a thing to happen ?? my wiring is ok . and all looks as it should . it just isnt charging on the car . any ideas ??

jharrison5

I never trust the parts store tests. Get a cheap multi-meter and while the car is running check the voltage coming out of the alt and also the voltage at the battery. If youre not seeing 13-15 volts then your alt is shot and if you do then trace the wires back to the battery and look for loose connections.

sofakingdom

iTrader: (1)

"Choke" (or some other idiot light other than SES) come on in the dash with key on and engine not running? If not, replace the bulb.

rusty vango

i have my own test rig , with the car running (which ,by the way is a 86 TPI car) it shows a no charge condition . but when i take it off and have it tested it charges ??? there is no "choke " light on it . the fuses are all good . and at the moment im stumped . heres the thing . with the key "on " there is 8 volts showing on the red wire and 1 volt showing on the brown wire . this is the two wire plug that plugs into the alt . i have battery voltage on the out put terminal. my FSM indicates a wiring issue , SOMEWHERE. any ideas ??

sofakingdom

iTrader: (1)

1V on the brown wire sounds about right. That should be near ground when the alt is not charging (which would light the light) and about the same as the big terminal when charging.

8V on the red wire may be part of the problem. That's the "sense" wire. Should have batt voltage on it, more or less. Should DEFINITELY have batt voltage, give or take, when running.

All of this, BTW, w the plug plugged in.

Re-check the same voltages when running, let's see what's doing what.

John in RI

iTrader: (167)

Did you paint the alternator or it's mounting brackets,..... I wonder if the alternator isn't getting a good ground ?? Might be a good idea to check the braided ground strap to be sure it's OK.


If the Red wire and the Red/Black wire are not providing full battery voltage than I'd also check the fusible link as well.


This is from an 85, I'm GUESSING that the 86 will be similar:




I used to test the old alternators like this: Start the car with everything connected - then disconnect the negative battery cable at the batery. Car stall or still running ?? The car should still run on the electricity produced by the alternator. If the car dies - then the alt can't produce enough voltage on it's own and should be replaced. ( this is not accurate for most newer cars ! )

sofakingdom

iTrader: (1)

Looks like the light bulb in question is labeled "Volts" according to John's FSM schematic.

Also, are the gauges working? If not, check the Gauges fuse; would have the same effect on charging as a bad bulb, if the fuse is blown.

rusty vango

gauges are working . cooling fan too ( which ,to me means that fusable link "d" is also good ). the car starts right up and runs well , no CEL either. it just isnt charging . im beginning to suspect the brown resistance wire. it would appear i have some wires to chase down

sofakingdom

iTrader: (1)

"Volts" indicator, as delineated on the schematic, light up with key on/engine off?

Checking the res wire is a piece o cake... unplug from the alt, pull the "Volts" light bulb out of the dash, measure ohms between the orange wire at the ign sw and the alt connector.

rusty vango

mine has the volt gauge, and it appears to be working along with the others , not sure if your test would still work ? and thanks for taking the time to reply

sofakingdom

iTrader: (1)

Yes of course, the cars w F motor all have a gauge.

According to the schematic, it still has a "Volts" (battery) idiot light. Doesn't say "optional", "equipped only in X model", or the like. Might wanna take your cluster bezel off, hold it up to the sunlight, find the lens with the little "Battery" icon (as shown on the schematic), and make sure there's a good bulb installed under it.

It's entirely possible that it has been burned out the entire time you've had the car, and for whyever, the alt has just now got around to caring about it.

The alt has to be fed enough power to start itself up, through the resistor and the bulb. If it doesn't get enough current it won't start even if it's "good". Which sounds like what your problem is: a "good" alt isn't working in your car. The 100 ohm resistor, by itself, probably doesn't feed it enough juice to get it going.

Yes the test will still work: follow the wires on the schematic. (I should have mentioned BTW, test w key off and batt disconn)

Examine the schematic. Believe the schematic. Trust the schematic. Do what the schematic tells you must be done. Don't start even thinking about hacking on wires until the parts they connect have been verified.

John in RI

iTrader: (167)

As much as I wish that were true,..... Shop manuals are not ALWAYS accurate. I remember realizing that the 86 shop manual contained the cluster printed circuit diagram,.... for an 82-85 Clusrter ! Heck; Last week I posted a 88 interior backlighting schematic for a guy and it completely omitted 1 of the interior lights - a full 2 years after it was added to the car !

ALL of the "Charging" diagrams in the 85 shop manual show that "Volts Indicator" light. That light was ONLY found on non-gauge clusters. Rather than stating that fact on all the drive-train diagrams,... they only made that note on the L4 schematic:

.

That diagram was posted to show the Charging system and doesn't show the volt gauge. The only reference I can find to the volt gauge itself in the 85 manual shows that the gauge gets it's power from the same "gauges" fuse Pin on the cluster and it looks like the gauge is grounded inside the cluster itself.



Something else I found weird,..... some years show the Brown wire @ F8 of C100 and labeled it as "charging" or "volts indicator"..... but other years show that this terminal was "not used". Not sure if this is because the non-gauge cluster was dropped in the late-eighties, or just another mistake in the diagrams.

rusty vango

yeah , i do not want to start hacking at all . i do have the FSM for my car . which i bought from the original owner in 09 . im off to do some tests . and thanks guys

Dyno Don

iTrader: (7)

Do this....with the alt on the car, engine running, touch voltage to the brown wire for an instant if the alt is good that should start it charging.

That is what they do on the bench when testing.

rusty vango

i had heard of that trick , good to hear it verified . but say i do that , and it works. does that mean i have something wrong ? (aside from the possible bad bulb in the cluster?)

rusty vango

sucess !! i found it , on my car the red wire in the 2 wire plug goes to the starter through a fusable link .... which just came apart in my hand. thanks to all who posted on this weirdness .

Dyno Don

iTrader: (7)

Good job

That was my next choice if it didn't charge.

John in RI

iTrader: (167)

These things can be such a PITA !! They almost always look OK and seem to be more and more prone to failure as time marches on !!

sofakingdom

iTrader: (1)

True: but OTOH, if you think THOSE are a PITA, just try dealing with an old rusty glass-tube fuse in a corroded cheeeeeeeeep holder, for some extra fun.

Glad you found it.

rusty vango

oh i can relate , my service truck is a 68 dodge A-108 van